Ongoing studies are currently investigating the factors that influence the efficacy of anti-estrogen, such as histological subtype (low-grade serous ovarian cancer), genetic signatures, high levels of estrogen and progesterone receptor expression, long treatment intervals (late recurrence beyond 24 months), and addition of aromatase inhibitors (versus other anti-estrogenic agents) [20,23]. Here, PGR is linked to ovarian serous adenocarcinoma.